This invention pertains to the continuous cobalt-catalyzed, liquid-phase oxidation of butane with oxygen and more particularly to the improvement of this process by limiting the amount of iron, water, and succinic acid by-product present while maintaining a minimum amount of cobalt acetate as a catalyst in the reaction mixture.
The oxidation of butane is a well-known process which has been described in numerous patents and technical publications relating to both liquid phase and vapor phase oxidation both catalytically and noncatalytically. U.S. Pat. No. 3,646,128 discloses an uncatalyzed butane oxidation process.
U.S. Pat. No. 3,923,882 discloses a butane oxidation process which utilizes ethanol as a promoter for the oxidation. U.S. Pat. No. 2,265,948 teaches a method of oxidizing normally gaseous saturated hydrocarbons in a liquid phase utilizing acetaldehyde as an initiator. U.S. Pat. No. 4,032,570 discloses a liquid phase process for converting butane to acetic acid with molecular oxygen and a cobalt catalyst while maintaining in the reaction zone all of the components of the reaction mixture including the water of reaction throughout the reaction period until a termination of the reaction.
U.S. Pat. No. 4,086,267 incorporates as an essential feature in the continuous oxidation of saturated aliphatic hydrocarbons with cobalt catalyst and oxygen, the feature in which a substantially gas free liquid is withdrawn from the base of the reaction zone and claims as an improvement using as the catalyst cobalt in the reaction zone in the +3 oxidation state. U.S. Pat. No. 4,131,741 claims an improved oxidation of saturated aliphatic hydrocarbons to acetic acid by limiting the residence time of the cobalt catalyst solution which is recycled so as to minimize the reduction of cobalt in the +3 oxidation state to cobalt in the +2 oxidation state.
In U.S. Pat. No. 4,131,742 a disclosure is made of the production of acetic acid by the oxidation of saturated aliphatic hydrocarbons with a cobalt catalyst in liquid phase in which a substantially gas free liquid is withdrawn from the base of the reaction zone and the reactor is fabricated from a substantially chromium-free material so that the level of chromium in the reaction medium is not greater than 400 ppm. In U.S. Pat. No. 3,196,182 an elongated reaction zone using plug flow of the reactants is used for producing oxygenated organic compounds by the liquid-phase oxidation of saturated aliphatic hydrocarbons.
U.S. Pat. No. 3,282,994 discloses a process for preparing acetic acid by the oxidation of butane which utilizes as a critical factor a reaction zone whose length to diameter ratio is less than about 15:1.
U.S. Pat. No. 3,646,128 discloses the oxidation of butane by a method which relies on using a liquid-separation zone wherein two liquid layers are obtained from the reaction zone for a work-up of the product.
U.S. Pat. No. 3,923,882 discloses the oxidation of butane in the liquid phase to provide acetic acid which utilizes ethanol as a promoter for the oxidation.
Despite the plethora of known processes for the catalytic, liquid-phase oxidation of butane to acetic acid there is still a need for a method of higher efficiency than those presently extant.